Diethyl ether
 Diethyl ether distilled from starting fluid
| |
| Names | |
|---|---|
| IUPAC name
Ethoxyethane
| |
| Other names
3-Oxapentane; Diethyl oxide; Dether; Ethyl ether; Ethyl oxide; Ethoxyethane; Solvent ether; Sweet oil of vitriol
| |
| Properties | |
| C4H10O (C2H5)2O | |
| Molar mass | 74.12 g/mol |
| Appearance | Colorless volatile liquid |
| Odor | Sweet eteric |
| Density | 0.7134 g/cm3 |
| Melting point | −116.3 °C (−177.3 °F; 156.8 K) |
| Boiling point | 34.6 °C (94.3 °F; 307.8 K) |
| 6.9 g/100 ml (20 °C) | |
| Solubility | Miscible with ethanol, methanol, hexane, hydrocarbons Immiscible with dimethyl sulfoxide |
| Vapor pressure | 440 mmHg (20 °C) |
| Viscosity | 0.224 cP (25 °C) |
| Thermochemistry | |
| Std molar
entropy (S |
253.5 J·mol-1·K-1 |
| Std enthalpy of
formation (ΔfH |
-271.2 ± 1.9 kJ/mol |
| Hazards | |
| Safety data sheet | Sigma-Aldrich |
| Flash point | −45 °C (-49 °F; 228 K) |
| Lethal dose or concentration (LD, LC): | |
| LD50 (Median dose)
|
73,000 ppm (rat, 2 hr) 6,500 ppm (mouse, 1.65 hr) |
| Related compounds | |
| Related compounds
|
Dimethyl ether Diisopropyl ether Tetrahydrofuran |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Diethyl ether is an organic compound with the chemical formula (C2H5)2O. It is a volatile colorless liquid at room temperature and is most commonly used in the lab as a nonpolar solvent. It is one of the most common ethers.
Contents
Properties
Chemical
Diethyl ether is commonly used as an extraction solvent, though it is rather expensive for use as such. It is often used as a solvent in Grignard reactions, however it must be dried and distilled over elemental sodium immediately prior to use. As with all ethers, it may hydrolyze to ethanol in contact with extremely strong bases or acids. Hydroiodic acid will cleave ethers.
Diethyl ether is highly flammable and will burn in open air.
- (CH3CH2)2O + 6 O2 → 4 CO2 + 5 H2O
Physical
Diethyl ether is a colorless liquid which is less dense than water. It is slightly soluble in water, and will dissolve an even lower amount of water. Diethyl ether is extremely volatile and thus, due to its nervous system depression effects, large amounts should only be used outside or in a fume hood. The volatility of diethyl ether and its reputation for high flammability make it one of the riskier solvents to make use of. It has a distinctive, sweet smell characteristic of ethers.
Availability
Diethyl ether is fairly widely available from chemical suppliers, however it is usually expensive. If reasonably pure but not reagent grade ether is acceptable, it can easily be distilled from many engine starter fluids found at automotive stores, gas stations, and department stores. It is often found alongside isomers of heptane, methylcyclohexane, and other hydrocarbons, but the very low boiling point of diethyl ether makes it easy to isolate.
Attention: do not spray the content of the can into a flask! This way, a lot of ether is lost (sciencemadness user Ave369 only distilled 50 ml of diethyl ether from a can of Quick-Start emptied that way). Penetrate the can accurately, let all the propellant gas out, then pour the content out.
A good tip is to cool the can in a freezer first, to limit the evaporation of the fluid, then carefully inject the chilled fluid in the distillation flask using the can's long straw or another plastic straw, if the can doesn't come with one.
A more direct approach involves carefully pinching the can with pliers, creating a very small hole through which the aerosol is allowed to be vented outside, while preventing the ether from being blown away.
Some types of starting fluid also have other impurities, like aldehydes (namely acetaldehyde), which usually come from the manufacturing process. They cannot be removed via distillation, but can be condensed by adding an alkali metal (like sodium) or a base (sodium hydroxide). After the whole solid polymerized, you should distill the product at least once more (you may filter the liquid if you desire), and this step should give you a much purer product. However, as some chemists have noted, even with a very large excess of NaOH or Na added to the impure ether, it takes weeks to completely remove the aldehydes from the starting fluid. The process can be sped up by stirring the mixture or even refluxing the crude ether, since the condensation products tend to coat the base or sodium metal, which further limits the reaction, or may even block it all together if the precipitate is thick enough.
Preparation
Diethyl ether is fairly easily prepared from concentrated sulfuric acid and azeotropic ethanol (though anhydrous works better), with the ether being distilled off.
- 2 CH3CH2OH → (CH3CH2)2O + H2O
A way to remove water is necessary for driving the reaction to completion, as the continual generation of water as a byproduct slows the reaction down. Care must be taken in this preparation, however, due to diethyl ether's incredibly high flammability and low flash point. Any distillation involving diethyl ether should not be walked away from. Boiling ether to dryness can cause explosions if sensitive peroxides are contained within, but this can be avoided by the addition of a small amount of higher-boiling solvent to the diethyl ether prior to distilling, such as mineral oil or glycerol. This additional solvent will be left behind post-distillation to solvate any peroxides and reduce their danger. This reaction must be performed between 135 °C and 150 °C to maintain an acceptable ether formation rate and reduce the production of ethylene gas.
Acetaldehyde is often a byproduct of the synthesis, and can be removed by destroying it with a strong base, like NaOH or KOH, which causes it to polymerize. Depending on the concentration of acetaldehyde, this step can take several days or weeks, as the condensed aldehydes will coat the NaOH flakes, slowing the reaction significantly. Strong stirring of the crude ether can speed up the purification process, as this breaks up the coating, while refluxing works even better.
Projects
- Destruction of styrofoam on contact
- Organic extractions
- Solvent for Grignard reactions and Grignard reagents
- Flamethrower
- Demonstration of the flash point of flammable liquids (can be done by touching a small pool of ether with a hot metal or glass rod)
Handling
Safety
Diethyl ether is highly flammable and can easily be ignited by electrical devices such as light switches, or hot surfaces such as hot plates. Due to its low flash and autoignition points, simply touching the ether with a red hot piece of glass or metal is enough to ignite it.
Diethyl ether vapors are also denser than air, and thus pool on the ground where hot surfaces are more likely to be present. Diethyl ether is also a slight nervous system depressant, however it does not present a significant health risk. It has narcotic properties and has been known to cause temporary dependence, condition sometimes referred to as etheromania.
Storage
Diethyl ether is best stored in narrow neck reagent glass bottles. Diethyl ether will slowly form explosive peroxides in storage, though addition of a small amount of butylated hydroxytoluene (BHT) or storage over sodium hydroxide will prevent this. Care must be taken not to distill ether to dryness due to the trace amounts of peroxides formed over time. Iron, copper, ferrous salts, and sulfites are known to inhibit the formation of peroxides.
Disposal
Diethyl ether can be safely burned, unless it has peroxides. If the ether tests positive for peroxides but there is no precipitate in the ether, it's possible to neutralize the dissolved peroxides. Reducing agents, like ferrous sulfate, sodium bisulfite or metabisulfite added in excess can be used to neutralize the peroxides. After neutralization, the ether should be tested again for peroxides and if none are present, it can be safely burned.
If it's a very old bottle, which has visible peroxide precipitated out of the solution, or one cannot estimate the age of the bottle, it is very likely to have peroxides on the cap. DO NOT OPEN THE BOTTLE! Instead take it to a remote of special area and safely detonate it. The latter may or may not require professional help, depending on the severity of the case.
However, if in the storage bottle a white-ish powdered precipitate appears after NaOH or KOH were added not long ago, this might just be just acetaldehyde condensed from the neutralization reaction. As the precipitate does not redissolve, it's best to just change the bottle if you're not sure you can't tell actual solid peroxides from metaldehyde.
